Provider Backbone Bridging, also referred to as Mac-in-Mac, has been standardized as IEEE 802.1ah-2008. Provider Backbone Bridging can allow isolation between different customer address spaces in Ethernet switches. Intermediate switches in a backbone domain can perform switching/forwarding of customer frames based on a backbone virtual local area network identifier, all without learning or using customer media-access control addresses. This isolation can be to the benefit of the customer at least from a security perspective, since the media-access control addresses of the customer are generally not learned or used for frame forwarding decisions in the core of a service provider network.